Research is made on the transformer vibration problem for real-time evaluation of transformer winding pressed state. A transformer tank vibration signal model is developed based on a study of the components of winding vibration

vibration transmission path and components of the tank surface vibration. It is found from transient excitation experiments that

relative to the front tank measuring points

the measuring points on the top surface reflect damping characteristics of the tank vibration better; the resonance frequency band of measuring point on the top surface and near the phase C casing is shifted to the left with the pressed force reduced. In the short-circuit experiments

by referring to a large number of experimental data in different current and pressed states

it is found that the distribution of resonance peaks of the measuring points on the top surface and near the phase C casing is consistent with the distribution of the resonance frequency band of measuring points on the top surface in the transient excitation experiments. The law of resonance spectra peak displacement is proposed for use in online evaluation of the transformer winding pressed state. The method is simple in which only the tank top surface vibration signal should be monitored. This method is adapted to the changing operating environment of the transformer with no electrical connection to the grid. Online evaluation of the transformer winding pressed state can be achieved. This work is supported by 2014 Key Scientific and Technological Projects of State Grid Jiangsu Electric Power Company (No. J2014055).